The present invention relates to a power window driving apparatus for controlling a power window installed in a vehicle, and more particularly to a technique for preventing an erroneous reversal of the power window when running on a rough and bumpy road.
A power window glass of a power window installed in the vehicle is connected to a driving motor and is operated to be raised or lowered by rotating reversibly the driving motor through operation of a switch. In addition, there has been proposed and put into practical use a power window having a function to prevent a damage to an obstacle and/or a power window glass itself that would be caused in the event that the obstacle is seized by the power window while it is being raised by stopping and then reversing the driving motor so as to lower the power window glass.
As a related power window driving apparatus, there has been known a technique for avoiding an impact caused by the seizure of an obstacle by the power window glass by stopping and reversing the driving motor when the value of a current flowing to the driving motor exceeds a predetermined value, whereby the driving motor is put in an excess load condition (see JP-A-10-25964 (FIG. 1), for example).
In the related power window driving apparatus described above, however, in the event that there occurs a variation in current which flows to the driving motor, irrespective of the fact that no seizure of obstacle by the power window glass occurs, it is determined that a seizure of an obstacle has occurred, and therefore, an erroneous operation is caused in which the power window is stopped and then is reversed.
This erroneous operation of the power window occurs very often when the vehicle is driven on rough roads and causes a problem that when running on a rough road, in the event that the window glass is raised, the driving force of the window glass is caused to vary due to vibrations (vertical vibrations) of the vehicle body, and due to this, the current flowing to the driving motor is caused to vary. As a result, there is caused a problem that the occurrence of a seizure of an obstacle by the power window is erroneously determined, whereby the power window is operated reversely.